Volatilization and Biodegradation of Naphthalene in the Vadose Zone Impacted by Phytoremediation

Abstract

The combined remediation mechanisms of volatilization and biodegradation in the vadose zone were investigated for naphthalene remediation at a creosote-contaminated site where a poplar tree-based phytoremediation system has been installed. Concurrent field and laboratory experiments were conducted to study the transport and biodegradation of naphthalene in the vadose zone. Soil gas sampling showed that more than 90% of the naphthalene vapors were biodegraded aerobically within 5-10 cm above the water table during the summer months. Peak naphthalene soil gas concentrations were observed in the late summer, corresponding with peak naphthalene aqueous concentrations and the minimum saturated zone thickness. An analytical solution was developed for vapor transport where the diffusion coefficient and first-order biodegradation rate vary vertically in two discrete zones. First-order aerobic biodegradation rates in laboratory columns using unsaturated site soil ranged from 5 to 28 days(-1) with a mean rate of 11 days(-1). The observed naphthalene mass flux at the source (3.3-22 microg cm(-2) d(-1)) was enhanced by aerobic biodegradation and was greater than the mean observed flux in the abiotic control column and the maximum theoretical mass flux by factors of 7 and 28, respectively.

Phytovolatilization of Organic Contaminants

“…At this site, a source area was located 2.4–3.7 m below ground surface, so reducing the saturated zone thickness substantially decreased the distance over which naphthalene diffused to the vadose zone, thereby increasing flux. Laboratory column studies and a 2-compartment model supported the field flux measurements . At two phytoremediation sites, Doucette et al measured TCE soil flux from both inside and outside of phytoremediation plots.…”

“…Laboratory column studies and a 2-compartment model supported the field flux measurements. 73 At two phytoremediation sites, Doucette et al 56 measured TCE soil flux from both inside and outside of phytoremediation plots. At one site, significant indirect phytovolatilization was observed, 69 Hong et al (MTBE), 63 Nzengung et al (PCE and TCE), 62 Orchard et al (TCE), 58 Yu and Gu (MTBE).…”

Biodegradation of cis-Dichloroethene and Vinyl Chloride in the Capillary Fringe

“…The moisture content in the microcosms was based on a previous study describing naphthalene biodegradation in the vadose zone (0.11 g of water/g of soil). 43 Controls were prepared without Polaromonas sp. JS666 or without MSB.…”

Study on adsorption and remediation of heavy metals by poplar and larch in contaminated soil

“…Besides heavy metals, the fast-growing species like genera Salix (willows and osiers) and Populus have also emerged as the most efficient species for phytoremediation of boron, PCBs, and naphthalene in contaminated soils (Robinson et al 2007;Liu and Schnoor 2008;Andersen et al 2008).…”